Heterogeneous azeotropic distillation ether dehydration separation and purification method

Abstract

The invention discloses a heterogeneous azeotropic distillation ether dehydration, separation and purification method, and belongs to the technical field of propylene glycol monomethyl ether and propylene glycol isomethyl ether recovery methods. An ether-water mixture is fed into an ether concentration tower through a first material flow pipeline, and the top of the ether concentration tower is communicated with a first condenser; the first condenser is connected with a middle feeding pipeline and is communicated with the middle of the azeotropic dehydration tower, the upper feeding pipeline is separated from the middle feeding pipeline and is communicated with the upper part of the ether azeotropic dehydration tower, a material discharged from the bottom of the ether azeotropic dehydration tower is communicated with a methyl ether product tower, and the liquid separation tank is connected with an azeotropic agent from the outside; an entrainer injection pipeline connected from the liquid separation tank is communicated with the middle of the ether azeotropic dehydration tower, a first branch pipeline connected from the entrainer injection pipeline is communicated with the top of the ether azeotropic dehydration tower, and second regulating valves are mounted on the entrainer injection pipeline and the second branch pipeline; the method solves the technical problems of large usage amount of benzene as an entrainer and difficulty in wastewater treatment in the prior art, and is mainly applied to separation and purification of the ether-water mixed solution.

Description

Technical Field

[0001] The invention belongs to the technical field of propylene glycol monomethyl ether and propylene glycol isomethyl ether recovery methods, and specifically relates to a method for separating propylene glycol monomethyl ether and isomethyl ether which are by-products in the process of producing propylene oxide by an HPPO process. Background Art

[0002] During the production of propylene oxide by the HPPO process, a large amount of propylene glycol monomethyl ether and propylene glycol isomethyl ether are produced as by-products, and the amount of the two is quite different at different reaction stages. The two have similar physical and chemical properties, and they co-exist with water, making their separation relatively difficult. Traditional separation methods generally use benzene as an azeotropic agent, and use benzene and water azeotropy to separate ether and water. However, since benzene is a primary carcinogen, leakage can easily cause environmental pollution and personal injury accidents. At the same time, the benzene and water azeotropic dehydration process requires a large amount of azeotropic agent and high energy consumption. A large amount of benzene is discharged with wastewater, which makes wastewater treatment difficult and the loss of azeotropic agent is large. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a method for dehydrating, separating and purifying ether by heterogeneous azeotropic distillation to solve the technical problems of large amount of benzene used as an azeotropic agent and difficulty in wastewater treatment in the prior art.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions: a method for dehydrating, separating and purifying ether by heterogeneous azeotropic distillation, characterized in that it includes an ether concentration tower, an ether azeotropic dehydration tower and a monomethyl ether product tower, the ether-water mixture is fed into the ether concentration tower through a first logistics pipeline, the ether concentration tower provides heat through a first reboiler, the ether concentration tower utilizes the difference in boiling points of the components in the ether-water mixture, when the ether-water mixture is heated, the ether with a lower boiling point is vaporized first, and the vaporized ether vapor rises in the tower, and in the rising process, the vapor and the reflux from the top of the tower are mixed. The reflux liquid coming down is fully heat exchanged on the tower plate. As the steam rises, the high boiling point components therein are gradually condensed and refluxed to the lower part of the tower, while the ether vapor continues to move upward. The top of the ether concentration tower is connected to the first condenser. After being condensed by the first condenser, the ether vapor becomes liquid. The first condenser is connected to the middle feed pipeline connected to the middle part of the azeotropic dehydration tower, and the upper feed pipeline separated from the middle feed pipeline is connected to the upper part of the azeotropic dehydration tower. The middle feed pipeline and the upper feed pipeline are installed with a first flow regulating valve;

[0005] The ether azeotropic dehydration tower provides heat through the second reboiler, and the bottom discharge of the ether azeotropic dehydration tower is connected to the methyl ether product tower;

[0006] The liquid separator is connected to an azeotropic agent from the outside, and the azeotropic agent is methylcyclohexane. The azeotropic agent injection pipeline is connected to the middle part of the ether azeotropic dehydration tower, and the azeotropic agent injection pipeline is connected to the first branch pipeline and connected to the top of the ether azeotropic dehydration tower. A second regulating valve is installed on the azeotropic agent injection pipeline and the second branch pipeline.

[0007] Furthermore: the first condenser is provided with a first non-condensable gas discharge line, the first non-condensable gas discharge line is connected to the top of the ether azeotropic dehydration tower, the top of the ether azeotropic dehydration tower is connected to the second condenser, the second condenser is connected to the separator, the separator is also connected to a wastewater pipeline, the wastewater pipeline is connected to the first logistics pipeline, after the first condenser condenses the ether vapor, the non-condensable gas is sent to the ether azeotropic dehydration tower from the first non-condensable gas discharge line, the methylcyclohexane entrainer and water at the top of the ether azeotropic dehydration tower are condensed by the second condenser and sent to the separator, after the liquid-liquid separation in the separator, the methylcyclohexane is sent to the ether azeotropic dehydration tower for reuse, and the wastewater containing part of the entrainer is sent to the first material pipeline through the wastewater pipeline to be mixed with the ether-water mixture and then sent to the ether concentration tower for concentration.

[0008] Furthermore: the opening of the first regulating valve on the middle feed pipeline and the upper feed pipeline is adjusted according to the concentration of monomethyl ether and isomethyl ether, the feed ratio of the middle feed pipeline to the upper feed pipeline is 6:4-8:2, and a concentration detection device can be installed on the middle feed pipeline to detect the concentration of monomethyl ether and isomethyl ether. The ether-water azeotrope condensed by the first condenser can also be collected for concentration detection. The opening of the first flow regulating valve on the middle feed pipeline and the upper feed pipeline is adjusted according to the concentration of propylene glycol monomethyl ether and propylene glycol isomethyl ether.

[0009] Furthermore: the injection amount of the entrainer pipeline is 1-5 times of the total feed amount.

[0010] Furthermore: the injection amount of the second branch pipeline is 2-6 times of the total feed amount.

[0011] Compared with the prior art, the present invention has the following advantages: 1. By adopting a new type of methylcyclohexane as an azeotropic agent and adjusting the feed position of the ether azeotropic dehydration tower, the water content of the propylene glycol monomethyl ether product is ≤ 0.01%, and the energy consumption of azeotropic distillation is reduced by more than 40%;

[0012] 2. By opening a first non-condensable gas pipeline at the top of the first condenser and condensing the liquid with the top of the ether azeotropic dehydration tower through the second condenser, the azeotropic agent is reused after liquid-liquid separation in the liquid separator. At the same time, the waste water containing the azeotropic agent is mixed with the ether-water mixture and sent to the ether concentration tower for reuse, thereby achieving zero loss of the azeotropic agent. Since the structure of the present application is more reasonable, the production cost is lower and it is suitable for comprehensive promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a flow chart of the present invention.

[0014] In the figure: 1. first logistics pipeline; 2. ether concentration tower; 3. first reboiler; 4. first condenser; 5. middle feed pipeline; 6. ether azeotropic dehydration tower; 7. upper feed pipeline; 8. first flow regulating valve; 9. second reboiler; 10. methyl ether product tower; 11. separator; 12. azeotropic agent injection pipeline; 13. first branch pipeline; 14. second regulating valve; 15. first non-condensable gas discharge line; 16. second condenser; 17. wastewater pipeline. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0016] In the description of the invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0017] In one embodiment, Figure 1 As shown, a heterogeneous azeotropic distillation ether dehydration separation and purification method is characterized in that it includes an ether concentration tower 2, an ether azeotropic dehydration tower 6 and a monomethyl ether product tower 10, the ether-water mixture is fed into the ether concentration tower 2 through a first logistics pipeline 1, the ether concentration tower 2 provides heat through a first reboiler 3, the top of the ether concentration tower 2 is connected to a first condenser 4, the first condenser 4 is connected to a middle feed pipeline 5 connected to the middle of the ether azeotropic dehydration tower 6, and an upper feed pipeline 7 separated from the middle feed pipeline 5, the upper feed pipeline 7 is connected to the upper part of the ether azeotropic dehydration tower 6, and a first flow regulating valve 8 is installed on the middle feed pipeline 5 and the upper feed pipeline 7;

[0018] The ether azeotropic dehydration tower 6 provides heat through the second reboiler 9, and the bottom discharge of the ether azeotropic dehydration tower 6 is connected to the methyl ether product tower 10;

[0019] The liquid separator 11 is connected to the entrainer from the outside, and the entrainer injection pipeline 12 is connected from the liquid separator 11 to the middle of the ether azeotropic dehydration tower 6, and the entrainer injection pipeline 12 is connected to the first branch pipeline 13 to the top of the ether azeotropic dehydration tower 6. A second regulating valve 14 is installed on the entrainer injection pipeline 12 and the second branch pipeline 13. The entrainer injection amount of the entrainer pipeline 12 is 1-5 times the total feed amount, and the entrainer injection amount of the second branch pipeline 13 is 2-6 times the total feed amount. The entrainer is methylcyclohexane;

[0020] The first condenser 4 is provided with a first non-condensable gas discharge line 15, the first non-condensable gas discharge line 15 is connected to the top of the ether azeotropic dehydration tower 6, the top of the ether azeotropic dehydration tower 6 is connected to the second condenser 16, and the second condenser 16 is connected to the liquid separation tank 1;

[0021] A concentration detection device can be installed on the optional middle feed pipeline 5 to detect the concentration of monomethyl ether and isomethyl ether or extract the ether-water azeotropic liquid to detect the concentration, and the opening of the first flow regulating valve 8 on the middle feed pipeline 5 and the upper feed pipeline 7 is adjusted according to the concentration of monomethyl ether and isomethyl ether. The feed ratio of the middle feed pipeline 5 to the upper feed pipeline 7 is 6:4-8:2;

[0022] The liquid separation tank 11 is also connected to a wastewater pipeline 17 , and the wastewater pipeline 17 is connected to the first logistics pipeline 1 .

[0023] The implementation method of the above scheme is as follows: in the initial working condition, the ether-water mixture in the HPPO process for producing propylene oxide is fed into the ether dehydration tower 2 through the first logistics pipeline 1, and the waste water is discharged from the bottom of the tower after being concentrated in the ether dehydration tower 2. The ether-water azeotrope at the top of the ether dehydration tower 2 is condensed by the first condenser 4, and the liquid enters the ether azeotropic dehydration tower 6 from the middle feed pipeline 5 and the upper feed pipeline 7 respectively. The methylcyclohexane entrainer in the liquid separator 11 is divided into two streams according to the proportion from the entrainer injection pipeline 12 and the first branch pipeline 13 are sent to the ether azeotropic dehydration tower 6. The top of the ether azeotropic dehydration tower 6 is a mixture of entrainer and water, which is condensed by the second condenser 16 and then sent to the separator 11. The separator 11 performs liquid-liquid separation on the entrainer and water. The separated wastewater still contains a small amount of entrainer. Therefore, during continuous operation, the entrainer-containing wastewater is mixed with the ether-water mixture of the first logistics pipeline 1 through the wastewater pipeline 17 and then sent to the ether concentration tower 2, thereby achieving zero loss of the entrainer.

[0024] Example 2: Based on the above-mentioned heterogeneous azeotropic distillation ether dehydration separation and purification method, this example is illustrated by an ether-water mixture consisting of water, monomethyl ether, isomethyl ether and propylene glycol, with a mass content of: water content: 70.29%, monomethyl ether: 8.05%, isomethyl ether: 19.92%, propylene glycol: 0.15; the ether-water mixture flow rate is 4300 kg / h, wherein:

[0025] Ether concentration tower 2: tower top pressure 0.08Mpa, tower top temperature: 114°C, tower bottom temperature: 118°C;

[0026] Ether azeotropic dehydration tower 6: tower top pressure: 0-20Kpa, tower top temperature: 73°C, tower bottom temperature: 123°C, methylcyclohexane is used as the azeotropic agent;

[0027] After the ether-water mixture is concentrated by the ether concentration tower 1, 4.3 t / h of ether-water azeotrope is produced, of which 2.7 t / h of ether-water azeotrope is fed into the ether azeotropic dehydration tower 6 from the upper feed port 7, 1.6 t / h of ether-water mixture is fed into the ether azeotropic dehydration tower 6 from the middle feed pipeline 5, 14.9 t / h of methylcyclohexane is injected into the top of the ether azeotropic dehydration tower 6 through the first branch pipeline 13, 4.7 t / h of methylcyclohexane is injected into the middle of the ether azeotropic dehydration tower 6 through the entrainer injection pipeline 12, 5.9 t / h of steam is consumed, and propylene glycol monomethyl ether and propylene glycol isomethyl ether in the bottom of the ether azeotropic dehydration tower 6 are fed into the monomethyl ether product tower, the water content of the monomethyl ether product is ≤0.01%, and there is no loss of entrainer.

[0028] Example 3: Based on the above-mentioned heterogeneous azeotropic distillation ether dehydration separation and purification method, this example is described with an ether-water mixture consisting of water, monomethyl ether, isomethyl ether and propylene glycol, with the following mass ratios: water content: 67.63%, monomethyl ether: 15.08%, isomethyl ether: 17.24%, propylene glycol: 0.05; the ether-water mixture flow rate is 4400 kg / h; wherein:

[0029] Ether concentration tower 2: tower top pressure 0.12Mpa, tower top temperature: 115℃, tower bottom temperature: 118℃;

[0030] Ether azeotropic dehydration tower 6: top pressure: 0-20Kpa, top temperature: 75℃, bottom temperature: 124℃, methylcyclohexane is used as azeotropic agent

[0031] After the ether-water mixture is concentrated by the ether concentration tower 1, 4.4 t / h of ether-water azeotrope is produced, of which 3.4 t / h of ether-water azeotrope is fed into the ether azeotropic dehydration tower 6 from the upper feed port 7, 1 t / h of ether-water mixture is fed into the ether azeotropic dehydration tower 6 from the middle feed pipeline 5, 16.7 t / h of methylcyclohexane is injected into the top of the ether azeotropic dehydration tower 6 through the first branch pipeline 13, 2.9 t / h of methylcyclohexane is injected into the middle of the ether azeotropic dehydration tower 6 through the entrainer injection pipeline 12, 6.3 t / h of steam is consumed, and propylene glycol monomethyl ether and propylene glycol isomethyl ether in the bottom of the ether azeotropic dehydration tower 6 are fed into the monomethyl ether product tower, the water content of the monomethyl ether product is ≤0.01%, and there is no loss of entrainer.

[0032] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements without departing from the principle of the present invention. These improvements should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for dehydrating, separating and purifying ether by heterogeneous azeotropic distillation, characterized in that: The invention comprises an ether concentration tower (2), an ether azeotropic dehydration tower (6) and a monomethyl ether product tower (10). The ether-water mixture is fed into the ether concentration tower (2) through a first logistics pipeline (1). The ether concentration tower (2) provides heat through a first reboiler (3). The top of the ether concentration tower (2) is connected to a first condenser (4). The first condenser (4) is connected to a middle feed pipeline (5) connected to the middle of the azeotropic dehydration tower (6). An upper feed pipeline (7) is separated from the middle feed pipeline (5). The upper feed pipeline (7) is connected to the upper part of the ether azeotropic dehydration tower (6). A first flow regulating valve (8) is installed on the middle feed pipeline (5) and the upper feed pipeline (7). The ether azeotropic dehydration tower (6) provides heat through the second reboiler (9), and the bottom discharge of the ether azeotropic dehydration tower (6) is connected to the methyl ether product tower (10); The liquid separator (11) is connected to an azeotropic agent from the outside, an azeotropic agent injection pipeline (12) is connected from the liquid separator (11) to communicate with the middle of the ether azeotropic dehydration tower (6), the azeotropic agent injection pipeline (12) is connected to a first branch pipeline (13) to communicate with the top of the ether azeotropic dehydration tower (6), and a second regulating valve (14) is installed on the azeotropic agent injection pipeline (12) and the second branch pipeline (13).

2. A method for dehydrating, separating and purifying ether by heterogeneous azeotropic distillation according to claim 1, characterized in that: The first condenser (4) is provided with a first non-condensable gas discharge line (15), the first non-condensable gas discharge line (15) is connected to the top of the ether azeotropic dehydration tower (6), the top of the ether azeotropic dehydration tower (6) is connected to the second condenser (16), and the second condenser (16) is connected to the liquid separation tank (1).

3. A method for dehydrating, separating and purifying ether by heterogeneous azeotropic distillation according to claim 2, characterized in that: The openings of the first flow regulating valves (8) on the middle feed pipeline (5) and the upper feed pipeline (7) are adjusted according to the concentrations of monomethyl ether and isomethyl ether. The feed ratio of the middle feed pipeline (5) to the upper feed pipeline (7) is 6:4-8:

2.

4. A method for dehydrating, separating and purifying ether by heterogeneous azeotropic distillation according to claim 3, characterized in that: The injection amount of the azeotropic agent pipeline (12) is 1-5 times of the total feed amount.

5. A method for dehydrating, separating and purifying ether by heterogeneous azeotropic distillation according to claim 3, characterized in that: The injection amount of the second branch pipeline (13) is 2-6 times of the total feed amount.

6. A method for dehydrating, separating and purifying ether by heterogeneous azeotropic distillation according to claim 2, characterized in that: The liquid separation tank (11) is also connected to a wastewater pipeline (17), and the wastewater pipeline (17) is connected to the first logistics pipeline (1).

7. The method for dehydrating, separating and purifying ether by heterogeneous azeotropic distillation according to claim 1, characterized in that: The entrainer is methylcyclohexane.

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